Overall, revenue growth above the trend-line for the past 16 years will continue in 2012 with some segments of staffing punching through pre-recession peaks.

U.S. staffing revenue rose 14 percent to $117.2 million in 2011 with growth higher-than-expected for this point in the business cycle, according to the new forecast by Staffing Industry Analysts, a sister organization of Workforce Management.

"In a year marked by modest GDP growth of 1.7 percent, the strong growth in temporary staffing revenue in 2011 is further evidence of a secular shift in demand above the expansion predicted by GDP growth, based upon the trend of the past 16 years," said Timothy Landhuis, research associate at Staffing Industry Analysts and author of the forecast.

Reasons for the shift in demand for temporary staffing include:

A snap-back in demand from steep recession declines.

A move away from independent contractors because of government crackdowns on misclassification.

Increased appreciation for agency temporaries among buyers as a result of the recession.

Overall, revenue growth above the trend-line for the past 16 years will continue in 2012 with some segments of staffing punching through pre-recession peaks.